Facile fabrication of flame-resistant, photothermal, and electrothermal polyurethane sponge: A promising sorbent for all-weather recovery of viscous crude oil spills from seawater

Herein, polyurethane (PU) sponges were modified by multi-walled carbon nanotubes (MWCNTs), hexagonal boron nitride@Fe3O4 (BNF), nano graphite (nG), and acrylic resin (AR) to prepare two photothermal and electrothermal converters as efficient crude oil sorbents. The PU/MWCNT/BNF/AR and PU/nG/BNF/AR com-posites were able to convert electric current and sunlight to heat energy. The generated heat energy increased crude oil mobility followed by increasing crude oil penetration into the sorbent. The results showed that three parameters of the composites, including their porosity, electrical conductivity, and thermal conductivity, affected the crude oil absorption capacity. Therefore, the PU/MWCNT/BNF/AR had better oil absorption capacity (83.5 g g-1) than PU/nG/BNF/AR in both heating methods due to its remarkable characteristics such as high porosity (96.13 %), high thermal conductivity (0.98 W m-1 K-1), and good electrical conductivity (1.33 x 10-1 S/m). In a continuous crude oil absorption process using a vacuum pump and applying a voltage of 4 V, the PU/MWCNT/ BNF/AR could absorb crude oil 72,170 times its own weight, which was the best amount among previously reported results. Moreover, the PU/MWCNT/BNF/AR was a superhydrophobic sponge with a water contact angle (WCA) of 165 degrees and had a UL94-V0 flammability rate as a high flame-resistant composite. These all-weather energy converters can be promising sorbents for heavy crude oil/water separation.